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Help with xover and port ideas for MTM project

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  • Help with xover and port ideas for MTM project

    I have a pair of powered monitors I bought from CSS a few years ago and I want to convert them to passive to be powered by my 2-channel Hypex UCD180 amp I am building.





    They are currently sealed, but I want to explore porting them (they don't make much bass at the moment). Internal dimensions are 7.5"x8.5"x13.5". The gear is:

    CSS RT1 ribbon (6 ohms)
    http://www.creativesound.ca/pdf/CSS-RT1-data-030508.pdf

    Tang-Band W4-1320SJF x2 (8 ohms each)
    https://www.parts-express.com/tang-b...eaker--264-915

    I was thinking of using a 3rd order xover @ 2500hz, but open to other ideas. I have a big bag of crossover parts, so I am definitely open to experimenting. I haven't done any enclosure modeling yet; last time I did was with WinISD many many years ago. What's the best tool to use now? They will be used in a smaller office in nearfield, no sub (for now). They don't need to be bass powerhouses, but a little kick would be nice. Any thoughts are greatly appreciated, thanks in advance!

  • #2
    WinISD is fine.

    Looks like the cabs are 0.5 cf each. W/a 2"id x 2" long port, a pair of those W4s should take 20w down into the 60s (should be plenty low to match up w/a future? sub). Most likely a full octave lower than they're running sealed. If the boxes are stuffed, you'd remove that and line the walls w/convoluted foam. Plug up the amp hole and put the vent behind the tweeter? 2.5k should work. Nothing wrong w/3k either.

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    • #3
      Thanks Chris, I really appreciate it. I believe they are already lined with convoluted foam, so that part is easy.

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      • #4
        Anyone know , under what condition the ribbons were measured in ? They look decent. Sorry not trying to hijack thread
        Attached Files

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        • #5
          Originally posted by nicholas_23 View Post
          Anyone know , under what condition the ribbons were measured in ? They look decent. Sorry not trying to hijack thread

          Comment


          • #6
            Try this for starters:

            3rd order HP: 2ohm series resistor and 6uF cap, 0.25mH shunt coil (to gnd. - a #20 is FINE), 18uF series cap. Negative polarity is indicated.
            2nd order LP: 0.80mH series coil (.4 ohm DCR in model), 8uF shunt cap.
            Fc just under 3k. About +4dBSC, about 90dB +/-1dB over ribbon's range.
            In YOUR 0.5cf box. 2"id x 2" port tunes to 70Hz w/an F3 under 60.

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            • #7
              Originally posted by Chris Roemer View Post
              Try this for starters:

              3rd order HP: 2ohm series resistor and 6uF cap, 0.25mH shunt coil (to gnd. - a #20 is FINE), 18uF series cap. Negative polarity is indicated.
              2nd order LP: 0.80mH series coil (.4 ohm DCR in model), 8uF shunt cap.
              Fc just under 3k. About +4dBSC, about 90dB +/-1dB over ribbon's range.
              In YOUR 0.5cf box. 2"id x 2" port tunes to 70Hz w/an F3 under 60.

              Comment

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